Multi-function chamber for a substrate processing system

ABSTRACT

A load lock chamber includes a chamber body having an aperture to allow a substrate to be transferred into or out of the chamber. The load lock chamber is configurable in several configurations, including a base configuration for providing a transition between two different pressures, a heating configuration for heating the substrate and providing a transition between two different pressures, and a cooling configuration for cooling the substrate and providing a transition between two different pressures. Various features of the chamber configurations help increase the throughput of the system by enabling rapid heating and cooling of substrates and simultaneous evacuation and venting of the chamber, and help compensate for thermal losses near the substrate edges, thereby providing a more uniform temperature across the substrate.

RELATED APPLICATIONS

This is a divisional of copending application (s) Ser. No. 09/502,117,filed on Feb. 10, 2000, which is a divisional of Ser. No. 09/082,375,filed May 20, 1998, now U.S. Pat. No. 6,086,362, issued Jul. 11, 2000.

The present application is related to co-pending U.S. patent applicationSer. No. 08/946,922, filed Oct. 8, 1997 and entitled “Modular On-LineProcessing System,” as well as the following U.S. patent applicationswhich are being filed concurrently with this application: (1) “Methodand Apparatus for Substrate Transfer and Processing” (2) “IsolationValves”; (3) “An Automated Substrate Processing System”; (4) “SubstrateTransfer Shuttle Having a Magnetic Drive”; (5) “Substrate TransferShuttle”; (6) “In-Situ Substrate Transfer Shuttle”; and (7) “ModularSubstrate Processing System”.

The foregoing patent applications, which are assigned to the assignee ofthe present application, are incorporated herein by reference in theirentirety.

BACKGROUND

The present invention relates generally to substrate processing systems,and, in particular, to a multi-function chamber for a substrateprocessing system.

Glass substrates are being used for applications such as active matrixtelevision and computer displays, among others. Each glass substrate canform multiple display monitors each of which contains more than amillion thin film transistors.

The processing of large glass substrates often involves the performanceof multiple sequential steps, including, for example, the performance ofchemical vapor deposition (CVD) processes, physical vapor deposition(PVD) processes, or etch processes. Systems for processing glasssubstrates can include one or more process chambers for performing thoseprocesses.

The glass substrates can have dimensions, for example, of 550 mm by 650mm. The trend is toward even larger substrate sizes, such as 650 mm by830 mm and larger, to allow more displays to be formed on the substrateor to allow larger displays to be produced. The larger sizes place evengreater demands on the capabilities of the processing systems.

Some of the basic processing techniques for depositing thin films on thelarge glass substrates are generally similar to those used, for example,in the processing of semiconductor wafers. Despite some of thesimilarities, however, a number of difficulties have been encountered inthe processing of large glass substrates that cannot be overcome in apractical way and cost effectively by using techniques currentlyemployed for semiconductor wafers and smaller glass substrates.

For example, efficient production line processing requires rapidmovement of the glass substrates from one work station to another, andbetween vacuum environments and atmospheric environments. The large sizeand shape of the glass substrates makes it difficult to transfer themfrom one position in the processing system to another. As a result,cluster tools suitable for vacuum processing of semiconductor wafers andsmaller glass substrates, such as substrates up to 550 mm by 650 mm, arenot well suited for the similar processing of larger glass substrates,such as 650 mm by 830 mm and above. Moreover, cluster tools require arelatively large floor space.

Similarly, chamber configurations designed for the processing ofrelatively small semiconductor wafers are not particularly suited forthe processing of these larger glass substrates. The chambers mustinclude apertures of sufficient size to permit the large substrates toenter or exit the chamber. Moreover, processing substrates in theprocess chambers typically must be performed in a vacuum or under lowpressure. Movement of glass substrates between processing chambers,thus, requires the use of valve mechanisms which are capable of closingthe especially wide apertures to provide vacuum-tight seals and whichalso must minimize contamination.

Furthermore, relatively few defects can cause an entire monitor formedon the substrate to be rejected. Therefore, reducing the occurrence ofdefects in the glass substrate when it is transferred from one positionto another is critical. Similarly, misalignment of the substrate as itis transferred and positioned within the processing system can cause theprocess uniformity to be compromised to the extent that one edge of theglass substrate is electrically non-functional once the glass has beenformed into a display. If the misalignment is severe enough, it even maycause the substrate to strike structures and break inside the vacuumchamber.

Other problems associated with the processing of large glass substratesarise due to their unique thermal properties. For example, therelatively low thermal conductivity of glass makes it more difficult toheat or cool the substrate uniformly. In particular, thermal losses nearthe edges of any large-area, thin substrate tend to be greater than nearthe center of the substrate, resulting in a non-uniform temperaturegradient across the substrate. The thermal properties of the glasssubstrate combined with its size, therefore, makes it more difficult toobtain uniform characteristics for the electronic components formed ondifferent portions of the surface of a processed substrate. Moreover,heating or cooling the substrates quickly and uniformly is moredifficult as a consequence of its poor thermal conductivity, therebyreducing the ability of the system to achieve a high throughput.

Depending on the functions or processes to be performed within aparticular process chamber, pre-poscessing or post-processing, such asheating or cooling of a substrate, may be required. Such pre-processingand post-processing functions may be performed in chambers separate froma primary process chamber. Due to the various functions that aparticular chamber is designed to perform, each chamber may beconfigured differently from other chambers. Moreover, once a chamber isdesigned to perform a particular function, such as pre-process heatingof the substrate, it may not be possible to reconfigure the chamber toperform another different function, such as post-process cooling of thesubstrate. Such designs can limit the flexibility offered by a givenchamber.

SUMMARY

In general, according to one aspect, an evacuable chamber includes achamber body having an aperture to allow a substrate to be;transferredinto or out of the chamber. The chamber is configurable using removablecomponents in at least two of the following configurations: a baseconfiguration for .providing a transition between two differentpressure, a heating configuration for heating the substrate andproviding a transition between two different pressures, and a coolingconfiguration for cooling the substrate and providing a transitionbetween two different pressures.

When the chamber is configured in the base configuration, the chamberincludes at least one removable volume reducing element. The removablevolume reducing elements can be made, for example, of plastic, aluminumor other vacuum-compatible material. One volume reducing element can bepositioned adjacent and below a lid of the chamber. Another volumereducing element can be positioned adjacent and above the bottominterior surface of the chamber.

When configured in the heating configuration, the chamber includes anupper heating assembly and a heating platen. The upper heating assemblycan be disposed between a lid of the chamber and a substrate supportmechanism. The heating platen can be movable to lift a substratepositioned on the support mechanism to a heating position below theupper heating assembly, and to lower the substrate from the heatingposition onto the support mechanism.

The heating platen can include inner and outer heating loops whosetemperatures are independently controllable. For example, duringoperation, the temperature of the outer loop can be maintained at ahigher temperature than the inner loop. The heating platen also can havean upper surface having a pattern of horizontal channels designed tocontrol a contact area between a substrate and the heating platen whenthe substrate is supported on the upper surface of the platen. Forexample, the concentration of channels can be greater near the center ofthe platen than near its perimeter.

The upper heating assembly can have a stationary plate with inner andouter heating loops whose temperatures can be controlled independentlyof one another. A gas delivery tube can be attached to the chamber, andthe stationary plate can include a series of vertical holes to allow agas to be delivered from the delivery tube to an interior region of thechamber via the vertical holes. The upper heating assembly also can havea diffusion screen disposed between the stationary plate and thesubstrate heating position.

Various of the foregoing features can help compensate for thermal lossesnear the edges of a large glass substrate and can provide a more uniformtemperature across the substrate when the chamber is configured in theheating configuration.

The heating configuration also can be used to perform ashing processes.

When configured in the cooling configuration, the chamber can include acooling platen and may also include an upper cooling assembly. When anupper cooling assembly is employed, it can be disposed between a lid ofthe chamber and a substrate support mechanism. The cooling platen can bemovable to lift a substrate positioned on the support mechanism to acooling position below the upper cooling assembly, and to lower thesubstrate from the cooling position onto the support mechanism.

The cooling platen can include multiple cooling tubes through which acooling fluid can flow. In one implementation, the concentration ofcooling tubes near the center of the platen can be greater than theconcentration near the perimeter. The cooling platen can have an uppersurface with a pattern of horizontal channels designed to control acontact area between a substrate and the cooling platen when thesubstrate is supported on the upper surface of the platen. In oneimplementation, the concentration of channels near the perimeter of thecooling platen is greater than near the center.

The upper cooling assembly also can have a stationary plate withmultiple cooling tubes through which a cooling fluid can be provided toflow. In some implementations, the concentration of cooling channels isgreater near the center of the stationary plate than near the perimeter.A gas delivery tube can be attached to the chamber. The stationary plateincludes a series of vertical holes to allow a gas to be delivered fromthe delivery tube to an interior region of the chamber via the verticalholes. The upper cooling assembly further can include a diffusion screendisposed between the stationary plate and the substrate coolingposition.

Various of the foregoing features can help compensate for, or take intoaccount, thermal losses near the edges of a large glass substrate andcan provide a more uniform temperature across the substrate when thechamber is configured in the cooling configuration.

Resistive elements can be provided to heat the chamber body and the lidto maintain them within a specified temperature range and to compensatefor thermal losses near the substrate edges. The resistive elements canbe used, for example, when the chamber is configured as a coolingchamber.

Water cooling can be provided to the chamber body and lid when thechamber is configured as a heating chamber if removal of excess heat isnecessary to limit and control temperature.

In yet a further aspect, a load lock chamber includes a chamber bodyhaving an aperture to allow a substrate to be transferred into or out ofthe chamber; and a thermally conductive platen for supporting asubstrate within the chamber. The platen has multiple zones forpreferentially changing the temperature of the substrate by conductionso as to compensate for thermal losses near edges of the substrate.

In addition, a method of processing a substrate in a load lock chamberincludes supporting the substrate on a substrate support mechanismwithin the chamber and changing the pressure in the chamber from a firstpressure to a second pressure. The method further includes controllingvarious surface temperatures in the chamber to compensate for, or takeinto account, thermal losses near edges of the substrate.

Various implementations include one or more of the following advantages.A single load lock chamber can be configured in multiple configurationsdepending on the requirements of the particular substrate processsystem. The chamber design, therefore, facilitates changes in systemdesign because the chamber can be re-configured relatively easily andquickly. Furthermore, the various configurations of the chamber allowtransitions between first and second pressures, such as atmospheric andprocess pressures, to be performed quickly.

Various features also enable a large glass substrate to be cooled orheated quickly, thereby increasing the throughput of the system.Depending on the particular configuration used, various features of thechamber design help compensate for thermal losses near the substrateedges to provide a more uniform temperature across substrate. Variousfeatures also can help maintain the edges of a substrate in compressionwhich can reduce the likelihood of substrate breakage during heating,cooling and other processes.

Additionally, the disclosed techniques for distributing a gas throughoutthe chamber provide improvements over prior techniques, which were notwell suited for handling large substrates.

Other features and advantages will be apparent from the followingdetailed description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan schematic view of a substrate processing system.

FIG. 2 is a cross-sectional view of a load lock chamber according to theinvention.

FIG. 3 is a cross-sectional view of the chamber of FIG. 2 configured asa base load lock chamber.

FIG. 4 is a cross-sectional view of the chamber of FIG. 2 configured asa heating or ashing load lock chamber.

FIG. 5 is an enlarged partial view of the chamber of FIG. 4.

FIG. 6 is a top view of a lower heating platen according to oneimplementation of the invention.

FIG. 7 is a top view of an upper heating assembly and chamber accordingto one implementation of the invention.

FIG. 8 is a top view of an upper heating assembly and chamber accordingto another implementation of the invention.

FIG. 9 is a cross-sectional view of the chamber of FIG. 2 configured asa cooling load lock chamber.

FIG. 10 is an enlarged partial view of the chamber of FIG. 9.

FIG. 11 is a top view of a lower cooling platen according to oneimplementation of the invention.

FIG. 12 is a top view of an upper cooling assembly according to oneimplementation of the invention.

DETAILED DESCRIPTION

As shown in FIG. 1, a glass substrate processing system may include oneor more islands 2. Each island 2 includes a first or input load lockchamber 4, one or more process chambers 6, and a second or output loadlock chamber 8. In various implementations, the process chamber 6 canbe, for example, a chemical vapor deposition (CVD) chamber, ea physicalvapor deposition (PVD) chamber, or an etch chamber.

Glass substrates, which can be on the order of one square meter, aretransferred, for example, by a continuous conveyor 10, to and from theisland 2 where one or more process steps can be performed sequentiallyto the substrate. An atmospheric loading robot 12 with an end effector14 can deliver substrates from the conveyor 10 to the input load lockchamber 4. Similarly, an atmospheric unloading robot 16 with an endeffector 18 can deliver substrates from the output load lock chamber 8to the conveyor 10. As illustrated in FIG. 1, a fresh substrate 20A isloaded into the load lock chamber 4 by the loading end effector 14, anda processed substrate 20B is removed from the load lock chamber 8 by theunloading end effector 18. A substrate transfer mechanism (not shown inFIG. 1) can transfer the substrates 20A, 20B between the variouschambers 4, 6 and 8 through apertures such as transfer or slit valves 5,7.

In general, substrate processing performed in the process chamber 6typically must be done under low pressure, or in a vacuum such asapproximately 10⁻⁸ Torr. Thus, the load lock chambers 4, 8 perform atransition between atmospheric pressure and the pressure in the processchamber 6. For example, the load lock chamber 4 can be pumped down to alow pressure, such as approximately 10⁻³ Torr, prior to transferring thesubstrate to the process chamber 6. Similarly, after the substrate istransferred from the process chamber 6 to the load lock chamber 8, theload lock chamber 8 can be brought to atmospheric pressure prior toopening the load lock chamber and transferring the substrate to theconveyor 10.

Referring to FIG. 2, an evacuable chamber 30, such as a load lockchamber, includes a temperature controlled chamber body 32 and atemperature controlled lid 34 attached to the chamber body. The chamberbody 32 and lid 34 can be formed, for example, of aluminum, and can beheated by coupling resistive elements 48 to the outer surfaces of thechamber body and lid. The temperature of the resistive elements 48 canbe controlled by a computer or other controller 66. An aperture 36 inone of the sidewalls of the chamber body 32 serves as a passageway fortransferring a substrate into or out of the load lock chamber 30. Theaperture 36 can be used, for example, when a substrate is transferredfrom the end effector 14 prior to processing or to the end effector 18after processing. A separate opening (not shown) in another one of thechamber sidewalls can be used to transfer the substrate between the loadlock chamber 30 and a process chamber, such as the process chamber 6(FIG. 1).

A substrate transfer and support mechanism 38 is disposed within theload lock chamber 30. The transfer and support mechanism 38 is used totransfer a substrate into and out of the load lock and can support thesubstrate within the chamber interior. In one implementation, thesubstrate transfer mechanism is a transfer shuttle, such as the shuttledescribed in the U.S. patent application referred to above, entitled“Method and Apparatus for Substrate Transfer and Processing.” During thetransition from atmospheric pressure to vacuum or some other processingpressure, the transfer mechanism 38 is cleaned of particles as the flowof gas in the load lock chamber 30 is directed past the transfermechanism prior to leaving the chamber through a vacuum port (not shown)in the bottom 40 of the chamber.

The chamber 30 also includes a gas delivery pipe or tube 42 throughwhich a gas can be delivered to the interior of the chamber 30.Additionally, the chamber 30 includes an aperture 44 extending throughthe bottom 40 of the chamber 30. As described below, thermocouples,heating elements and/or a water line can be provided to the interior ofthe chamber through the aperture 44. In some implementations, theaperture 44 is closed or sealed.

As described in greater detail below, the load lock chamber 30 can beconfigured in at least the following configurations: a baseconfiguration for providing a transition between two differentpressures, a heating configuration for heating the substrate andproviding a transition between two different pressures, or a coolingconfiguration for cooling the substrate and providing a transitionbetween two different pressures. The load lock chamber 30 also can beconfigured in an ashing configuration. In general, the chamber 30 can beconfigured in at least two of the foregoing configurations. Furthermore,the load lock chamber 30 can be re-configured relatively easily from oneconfiguration to another configuration.

The chamber 30 can be configured as a base load lock chamber 30A (FIG.3) which can be used, for example, for transitions between first andsecond pressures, such as atmospheric pressure and a processingpressure. In the base configuration, one or more removable volumereducing elements 50A, 50B are added to the interior of the chamber 30A.In the illustrated implementation, an upper volume reducing element 50Ais disposed adjacent and below the lid 34 and a lower volume reducingelement 50B is disposed adjacent and above a bottom interior surface ofthe chamber. The mechanism 38 which supports the substrate is positionedbetween the upper and lower volume reducing elements 50A, 50B. In oneimplementation, the volume reducing elements 50A, 50B can berectangular-shaped and can be formed, for example, of a plastic materialsuch as LEXAN or aluminum. In general, the volume reducing elements 50A,50B are designed to be as large as possible without interfering with theoperation of the transfer mechanism 38 or the end effectors 14, 18 ofthe robots 12, 16 (FIG. 1) when the substrate is transferred from oneposition to another. The upper volume reducing element 50A can beattached to the chamber lid 34, for example, with screws, bolts or pins.The lower volume reducing element 50B can rest on the chamber floor.

One advantage of using the volume reducing elements 50A, 50B is thatwhen the chamber 30A is used as an input load lock chamber, the pressurein the chamber can be pumped down to the processing pressure morequickly, thereby increasing the throughput of the system. Similarly,when the chamber 30A is used as an output-load lock chamber, thepressure in the chamber can be brought back to atmospheric pressure morequickly. Furthermore, when the chamber 30A is used as an output loadlock chamber, an inert gas such as nitrogen or argon, is provided to thechamber interior, via the gas delivery tube 42, to provide thetransition to atmospheric pressure. For this purpose, the upper volumereducing element 50A can include one or more vertical channels 52 thatallow the gas to be provided to an interior region of the chamber. Theupper surface of the volume reducing element 50 A also can includehorizontal channels (not shown) that allow the gas to flow from thedelivery tube 42 to the vertical channels 52.

In some etch systems, substrates are maintained at temperatures of lessthan approximately 100° C. The base configuration is suitable, forexample, as either the input or output load lock chamber in such etchsystems.

The chamber 30 (FIG. 2) can also be configured as a heating load lockchamber 30B (FIGS. 4-7). In the heating configuration, the volumereducing elements 50A, 50B are removed, and are replaced by a removableupper heating assembly 56 and a removable lower heating. platen 54,respectively. The upper heating assembly 56, which is described ingreater detail below, can be attached to the chamber lid 34, forexample, by shoulder screws, clamps, or bolts.

The lower heating platen 54 is a vertically movable temperaturecontrolled hot plate, which can be formed, for example, from stainlesssteel. When a substrate is placed on the lower platen 54, the lowerplaten conducts heat directly into the substrate. The lower platen 54includes an inner heating loop 58A and an outer heating loop 58B, eachof which has one or more heating elements, such as coils. The heatingelements for the inner and outer loops 58A, 58B can be coupled to thecontroller 66 by connections 62 through a tube 46 which extend throughthe aperture 44 30 and which is welded to the lower platen 54.Thermocouples for measuring the temperature of the lower platen 54 alsocan be connected from the platen 54 to the controller 66 by connections64 through the tube 46. The tube 46 can be surrounded by a bellows (notshown) to provide a vacuum seal within the chamber when the platen 54moves vertically.

The temperature of the inner and outer heating loops 58A, 58B can becontrolled independently. The independent temperature control allows thesurface of the platen 54 near its perimeter to be maintained at adifferent temperature from the surface of the platen near its center. Inone implementation, the temperature of the outer loop 58B is maintainedat a higher temperature than the inner loop 58A. Such a temperaturedifference helps compensate for the heat loss in the substrate near itsedges and helps reduce the possibility of substrate breakage due tocracks propagating through the substrate as a result of edge defects.Rapid heating of substrates is, therefore, facilitated.

The upper surface of the lower platen 54 includes a pattern of one ormore horizontal grooves or channels 60 (FIGS. 5-6). In oneimplementation, two sets of channels 60 are formed across the surface ofthe lower platen 54 with one set of channels formed radially and theother set formed circularly. In the illustrated implementation, thechannels 60 have a width of about 6 mm and a depth of about 1 mm. Otherdimensions may be suitable for particular applications. The spacingbetween adjacent channels, or the concentration of the channels, isdesigned to control the contact area between a substrate and the platen54 and provides further control of the temperature gradient across thesubstrate. For example, in one implementation, fewer channels 60 perunit area are provided near the perimeter of the platen 54 compared tothe number of channels near the center of the platen. Such a patternincreases the contact area between the platen and a surface of thesubstrate near the substrate edges compared to the contact area betweenthe platen and a surface of the substrate near the substrate center.Therefore, the pattern of channels 60 also can help compensate forthermal losses near the edges of the substrate to provide a more uniformtemperature profile across the substrate.

In operation, according to one implementation, an external robot, suchas the robot 12 (FIG. 1), loads a substrate into the heating load lockchamber 30B and places the substrate onto the transfer mechanism 38. Thelower heating platen 54 is raised and lifts the substrate off thetransfer mechanism 38. The platen 54 continues rising until thesubstrate is brought to a heating position. The heating position shouldbe as close as possible to the position in which the thermal losses fromthe edges of the substrate to the cooler walls of the chamber body 32are minimized. In one implementation, for example, the substrate can belifted to within several millimeters of the upper heating assembly 56 sothat the viewing angle of the substrate edge with respect to the chamberwalls is reduced as much as possible. As the chamber is heated, coolingwater tubes with an appropriate degree of thermal contact to the outerwalls of the chamber help maintain the temperature of the chamber wallswithin a desired range and prevent the walls from becoming too hot. Thecooling tubes may be joined to a plate which is affixed to the chamberwalls. For example, in one implementation, the temperature of thechamber walls is maintained at approximately 100° C. In addition,thermal barriers can be provided along the outside walls of the chamberto protect workers or others from touching the hot chamber surfaces.

As the lower platen 54 lifts the substrate off from the transfermechanism 38 and raises it to the heating position, some of the channels60 on the upper surface of the platen and holes through the platen allowgas that is between the platen and the substrate to escape. The channels60 and holes thus help prevent the formation of a trapped cushion of gasthat could cause the substrate to float and drift from its initialdesired position on the platen 54.

The upper heating assembly 56 includes a stationary plate 68, which canbe made of stainless steel and which includes an inner heating loop 69Aand an outer heating loop 69B, each of which has one or more heatingelements, such as coils. The temperature of the loops 69A, 69B can becontrolled so as to obtain a more uniform temperature across thesubstrate. Thermocouples can be attached to the plate 68 for measuringits temperature. The thermocouples and heating elements can be coupledto the controller 66 by connections 70 and 72, respectively.

The stationary plate 68 further includes a series of vertical holes 78(FIG. 7) which are formed through the plate 68. In the illustratedimplementation, an outer zone 78A of holes 78 and an inner zone 78B ofholes are formed through the plate 68. The heating assembly 56 alsoincludes a diffusion screen 74 (FIG. 5) which can comprise one or morefine mesh screens or filters with multiple holes. The diffusion screen74 is mounted to the stationary plate 68, for example, by a clamp 76.

Once a substrate is moved to its heating position in the chamber 30B,the upper heating assembly 56 heats the substrate primarily byconduction and radiation. Using an upper heater assembly which has zonesof various emissivities on the surface facing the substrate can be usedto facilitate the substrate heating rate, and thermal uniformity can becontrolled. An inert gas, such as nitrogen or argon, can be introducedfrom a gas source 100A via the delivery tube 42 to the back-side orupper surface 80 of the plate 68 to facilitate the heating processfurther. The gas flows along the upper surface 80 of the plate 68 towardthe holes 78. The gas, which is heated as it flows along the uppersurface 80, then can pass through the holes 78 to the front-side orlower surface of the plate 68. The amount of gas flow exiting from theinner and outer zones 78A, 78B relative to one another into the chambercan be changed by varying the size or the number of holes 78 in thestationary plate 68, as well as by varying the gas pressure in thezones.

Once the gas flows to the front-side of the plate 68, the diffusionscreen 74 directs the gas onto the substrate surface facing the heatingassembly 56. The diffusion screen 74 can restrict the flow of the gas tolimit disturbances that otherwise may be caused as the gas flows ontothe substrate. The diffusion screen 74 also can bias the heat transferto the substrate to improve the uniformity of the substrate temperature.For example, the diffusion screen 74 preferentially can introduce more(or less) gas near the outer portions of the chamber to provide a moreuniform temperature across the substrate. If a diffusion screen is notused, the gas flows directly on to the substrate.

The configuration of FIGS. 4-7 can be used, for example, as an inputload lock chamber in which a substrate is heated prior to beingtransferred to a process chamber. Such pre-process heating may berequired or desirable, for example, in CVD and PVD systems, as well asother substrate processing systems. When the load lock chamber 30D isused as an input chamber to heat the substrate prior to its transfer toa process chamber, the amount and extent of gas flow from the deliverytube 42 may need to be regulated or limited to allow the chamber 30B tobe pumped down to a vacuum or some other process pressure.

Once the desired heating of the substrate occurs, the platen 54 islowered, allowing the substrate to be transferred back to the transfermechanism 38. The substrate then can be transferred by the transfermechanism 38, for example, to the process chamber 6.

The chamber.30B also can be used as an ash load lock chamber. In such anapplication, the inert gas source 100 is replaced by an ash gas source100B (FIG. 8). Such a configuration can be used, for example, as anoutput load lock chamber where, in addition to providing a transition toatmospheric pressure, a post-process ash takes place. In oneimplementation, the chamber 30B can be used as an ash load lock to ash aphotoresist layer on a substrate that is received from a primary processchamber, such as the chamber 6 (FIG. 1).

When the chamber 30B is configured as an ash load lock chamber, thechamber is typically heated to a lower temperature than when the chamberis used as an input heating load lock. In one exemplary application, thecontroller 66 heats the chamber 30B to approximately 150° C., and an ashgas, such as oxygen (O₂) or carbon tetra fluoride (CF₄), is provided tothe chamber interior via the delivery tube 42. Once the ashing processis completed, the load lock is pumped, purged and vented to atmosphericpressure. The substrate then can be transferred, for example, by therobot 16 to the conveyor 10.

The chamber 30 (FIG. 2) also can be configured as a cooling load lockchamber 30C (FIGS. 9-12). The cooling configuration 30C includes aremovable upper cooling assembly 86 and a removable lower cooling platen84. The upper cooling assembly 86, which is described in greater detailbelow, can be attached to the chamber lid 34, for example, by shoulderscrews, clamps or bolts.

The lower cooling platen 84 is a vertically movable temperaturecontrolled cooling plate, which can be formed, for example, fromstainless steel or aluminum. When a substrate is placed on the lowerplaten 84, the lower platen conducts heat directly from the substrate,thereby cooling the substrate. When temperatures of the chamber wallsand arriving substrates are sufficiently low, the lower platen may havesufficient heat loss to the chamber to allow continuous operationwithout the need to be actively cooled, for example, by running waterthrough it. When necessary, however, the lower platen 84 includesmultiple cooling tubes 92 through which a cooling fluid, such as water,can flow. The water can be provided to the cooling tubes 92 through astainless steel water line 82 which extends through the aperture 44 andwhich is welded to the lower platen 84. The controller 66 can controlthe flow of water through the water line 82 to the tubes 92. The waterline 82 can be surrounded by a bellows (not shown) to maintain thepressure within the chamber when the platen 84 moves vertically asdescribed below. The position and concentration of the cooling tubes 92is selected to obtain a more uniform temperature profile across thesubstrate by taking into account or compensating for thermal losses nearthe edges of the substrate. Thus, for example, the concentration ofcooling tubes 92 near the center of the platen 84 can be greater thanthe concentration near its perimeter. Such a configuration can provide amore uniform temperature profile throughout the substrate, can helpreduce the likelihood of substrate breakage, and can facilitate therapid cooling of the substrate in the load lock chamber 30C.

The upper surface of the lower platen 84 includes a pattern of one ormore horizontal grooves or channels 90 (FIGS. 10-11). In oneimplementation, two sets of channels 90 are formed across the surface ofthe lower platen 84 with one set of channels formed substantiallyperpendicular to the other set. In the illustrated implementation, thechannels 90 have a width of about 6 mm and a depth of about 1 mm. Otherdimensions may be suitable for particular applications. The spacingbetween the channels 90, or the concentration of the channels, isdesigned to control the contact area between a substrate and the platen84 and provides further control of the temperature gradient across thesubstrate. For example, in one implementation, more channels 90 per unitarea are provided near the perimeter of the platen 84 compared to thenumber of channels per unit area near the center of the platen. Such apattern increases the contact area between the platen 84 and a firstsurface of the substrate near its center compared to the contact areabetween the platen and a second surface of the substrate near itsperimeter where the first and second areas are the same size. Ingeneral, the pattern of channels 90 on the platen 84 can be designed totake into account or compensate for thermal losses near the edges of thesubstrate so as to provide a more uniform temperature profile throughoutthe substrate.

In operation, according to one implementation, a substrate is loadedfrom a process chamber, such as the chamber 6 (FIG. 1), onto thetransfer mechanism 38 in the cooling load lock chamber 30C. The lowercooling platen 84 is raised and lifts the substrate off the transfermechanism 38. The platen 84 continues rising until the substrate isbrought to a cooling position. The substrate can be lifted, for example,to within several millimeters of the upper cooling assembly 86 so thatthe viewing angle of the substrate edge with respect to the chamberwalls is reduced as much as possible when the substrate is in itscooling position.

The upper cooling assembly 86 includes a stationary plate 98, which canbe made of stainless steel or aluminum and which includes multiplecooling tubes 102 through which a cooling fluid, such as water, canflow. The configuration of the cooling tubes 102 also is designed toprovide a more uniform temperature throughout the substrate by takinginto account or compensating for thermal losses near the edges of thesubstrate. In one implementation, the concentration of the coolingchannels is greater near the center of the plate than near itsperimeter.

The stationary plate 98 further includes a series of vertical holes 108(FIG. 12) which are formed through the plate 98. In the illustratedimplementation, an outer zone 108A of holes 108 and an inner zone 108Bof holes 108 are formed through the plate 98. The upper cooling assembly86 also includes a diffusion screen 104 (FIG. 10) which can comprise oneor more fine mesh screens or filters having multiple holes. In someimplementations, the diffusion screen 104 preferentially can introducemore (or less) gas near the center of the chamber relative to otherparts of the chamber. The diffusion screen 104 is mounted to thestationary plate 98, for example, by a clamp 106.

Once a substrate is moved to its cooling position in the chamber 30C,the upper cooling assembly 86 helps cool the substrate primarily byforced convection and radiation processes. Zones of various emissivitieson the surface of the upper cooling assembly facing the substrate alsocan be used to facilitate the cooling process and tailor thermaluniformity. An inert gas, such as nitrogen or argon, can be introducedfrom a gas source 100C via the delivery tube 42 to the back-side orupper surface 110 of the plate 98 to facilitate the cooling processfurther. The gas flows along the upper surface 110 of the plate 98toward the holes 108. The gas, which is cooled as it flows along theupper surface 110, then can pass through the holes 108 to the front-sideor lower surface of the plate 98. The amount of gas flow exiting fromthe inner and outer zones 108A, 108B relative to one another into thechamber can be changed by varying 10 the size or the number of holes 108in the stationary plate 98, as well as by varying the gas pressure inthe zones. Water-cooling the stationary plate may not always berequired. When it is not, the stationary plate acts to distribute thegas flow to the back or upper side of the diffusion screen 104.

The diffusion screen 104 directs the gas onto the substrate surfacefacing the upper cooling assembly 86. The diffusion screen 104 canrestrict and distribute the flow of the gas to limit turbulence and eddyflows that otherwise may be present as the gas flows onto the substrate.The diffusion screen 104 also can control the flow of gas to help biasheat transfer from the substrate. The diffusion screen can be designed,for example, so that the flow of the gas results in a more uniformtemperature profile across the substrate.

When configured as a cooling load lock chamber, the chamber body 32 andlid 34 also can be heated using the resistive elements 48 to maintaintheir temperature within a specified range above the cooling watertemperature. In one implementation, the temperature of the chamber wallsis maintained at approximately 100° C. Heating the walls of the chamberbody 32 during a cooling process can provide several advantages. First,such heating can compensate for the thermal losses near the substrateedges, thereby providing a more uniform temperature profile across thesubstrate as it cools. Furthermore, such heating can help reduceadsorption of water vapor on the chamber walls while the chamber is openduring substrate removal. Reducing the amount of water vapor can preventthe water vapor from combining with residual by-products from theprocess chamber 6, such as chlorine gas (Cl₂). Preventing thecombination of water vapor and such residual by-products is importantbecause the combination of such. chemicals can cause corrosion of thechamber 30C. Additionally, when the cooling load lock is arrangedadjacent a process chamber in which heating of the walls is desirable ornecessary, the hot surfaces of the chamber body also prevent the coolingload lock from acting as a heat sink and drawing heat from the processchamber.

The configuration of FIGS. 9-12 can be used, for example, as an outputload lock chamber in which a substrate is cooled and the chamber isreturned to atmospheric pressure prior to being transferred to theconveyor 10 (FIG. 1). Such post-process cooling may be required ordesirable, for example, in CVD or PVD systems where processingtemperatures may reach 200-450° C. To accelerate the transition toatmospheric pressure, an inert gas such as nitrogen or argon can beprovided to the chamber 30C from the delivery tube 42. The channels 90in the upper surface of the lower cooling platen 84 and holes throughthe platen allow gas to reach the backside of the substrate whichfacilitates separating the substrate from the platen. The substrate thencan be transferred to the transfer mechanism 38 and to the conveyor 10(FIG. 1).

Although the control system is shown as a single controller 66, thecontrol system can include multiple dedicated controllers to controlsuch features as the movement of the lower platens 54, 84, as well asthe temperature of the lower platens, the temperature of the upperassemblies 56, 86, the temperature of the chamber body 32 and chamberlid 34, the flow of a cooling fluid through the line 82, and the flow ofgas through the gas tube 42.

As described above, a single load lock chamber 30 (FIG. 1) can beconfigured in multiple configurations depending on the requirements ofthe particular substrate process system. The chamber design, therefore,facilitates changes in system design because the chamber 30 can bere-configured relatively easily and quickly. Furthermore, the variousconfigurations of the chamber 30 allow transitions between first andsecond pressures, such as atmospheric and process pressures, to beperformed quickly.

Various features of the load lock chamber can provide a more uniformtemperature across a substrate as it is heated or cooled. Although it isdesirable to obtain a perfectly uniform temperature across thesubstrate, it is difficult, if not impossible, to achieve such perfectuniformity in practice. Accordingly, various features of the load lockare designed to ensure that portions of the substrate near its edges aremaintained at a temperature at least as high as the temperatures inother portions of the substrate. Such features result in a slightcompressive force to the edges of the substrate and help reduce thelikelihood of substrate breakage in the chamber. The variousconfigurations also enable a substrate to be cooled or heated quickly,thereby increasing the throughput of the system.

Other implementations are within the scope of the following claims.

What is claimed is:
 1. A method of processing a substrate in aprocessing chamber, the method comprising: decreasing the volume of thechamber from a first processing volume to a second processing volume;supporting the substrate on a substrate support mechanism within thechamber; changing the pressure in the chamber from a first pressure to asecond pressure; and controlling surface temperatures in the chamber tocompensate for thermal losses near edges of the substrate.
 2. The methodof claim 1, further comprising heating the substrate in the processingchamber by conduction.
 3. The method of claim 2, further comprisingtransferring the substrate from the support mechanism onto a heatingplaten.
 4. The method of claim 1 further comprising heating thesubstrate in the processing chamber by radiation.
 5. The method of claim4, wherein heating the substrate by radiation comprises: raising thesubstrate to a heating position near a stationary plate; and heating thestationary plate so that the plate has a temperature gradient thatgenerally increases from a point near a center of the plate to a pointnear a perimeter of the plate.
 6. The method of claim 1, furthercomprising: transferring the substrate from the support mechanism onto aheating platen; and moving the heating platen to a position within thechamber to reduce a viewing angle of the substrate edge with respect towalls of the chamber.
 7. The method of claim 1, wherein decreasing thevolume of the chamber comprises positioning at least one volume reducingelement therein.
 8. The method of claim 7, wherein the volume reducingelement comprises materials selected from plastics, metals, andcombinations thereof.
 9. The method of claim 7, further comprisingreplacing the volume reducing element with at least one heatingassembly.
 10. The method of claim 9, further comprising positioning atleast one heating assembly above the substrate support.
 11. The methodof claim 9, further comprising positioning the at least one heatingassembly below the substrate support.
 12. The method of claim 11,wherein controlling surface temperatures in the chamber comprisesmaintaining a higher temperature near the periphery of the heatingassembly with respect to the center of the heating assembly.
 13. Themethod of claim 12, wherein maintaining a higher temperature near theperiphery of the heating assembly with respect to the center of theheating assembly comprises heating at least one outer heating loop ofthe heating assembly to a higher temperature with respect to at leastone inner heating loop of the heating assembly.
 14. The method of claim7 further comprising configuring the processing chamber as a load lockchamber.
 15. The method of claim 14, further comprising configuring theload lock chamber as an input load lock chamber and wherein the firstpressure is atmospheric pressure and the second pressure is a processingpressure.
 16. The method of claim 14, further comprising configuring theload lock chamber as an output load lock chamber and wherein the firstpressure is a processing pressure and the second pressure is atmosphericpressure.
 17. The method of claim 14, further comprising providing a gasto the chamber to transition the first pressure to the second pressure.18. The method of claim 17, wherein the gas comprises an inert gas. 19.The method of claim 17, wherein the gas comprises nitrogen, argon, andcombinations thereof.
 20. A method of processing a substrate in aprocessing chamber, comprising: decreasing the volume of the chamberfrom a first processing volume to a second processing volume; supportingthe substrate on a substrate support mechanism within the chamber;changing the pressure in the chamber from a first pressure to a secondpressure; controlling surface temperatures in the chamber to compensatefor thermal losses near edges of the substrate; and heating thesubstrate in the processing chamber by conduction, wherein heating thesubstrate comprises transferring the substrate from the substratesupport mechanism onto a heating platen and heating the platen so thatan upper surface of the platen has a temperature gradient that generallyincreases from a point near a center of the platen to a point near aperimeter of the platen.
 21. The method of claim 20, wherein decreasingthe volume of the chamber from a first processing volume to a secondprocessing volume comprises positioning at least one volume reducingelement therein.
 22. The method of claim 21, further comprisingreplacing the volume reducing element with a heating assembly.
 23. Amethod of processing a substrate in a processing chamber, comprising:decreasing the volume of the chamber from a first processing volume to asecond processing volume; supporting the substrate on a substratesupport mechanism within the chamber; changing the pressure in thechamber from a first pressure to a second pressure; controlling surfacetemperatures in the chamber to compensate for thermal losses near edgesof the substrate; and heating the substrate in the processing chamber byconduction, wherein heating the substrate comprises: transferring thesubstrate from the substrate support mechanism onto a heating platen;heating the platen so that an upper surface of the platen has atemperature gradient that generally increases from a point near a centerof the platen to a point near a perimeter of the platen; and providing acontact area between the upper surface of the platen and a first surfacearea of the substrate near the perimeter of the substrate that isgreater than a contact area between the upper surface of the platen anda second surface area of the substrate near the center of the substrate,wherein the first and second surface areas of the substrate are the samesize.
 24. The method of claim 23, wherein decreasing the volume of thechamber from a first processing volume to a second processing volumecomprises positioning at least one volume reducing element therein. 25.The method of claim 24, further comprising replacing the volume reducingelement with a heating assembly.